在初中演示实验中,集中学生注意、启迪思维的几点做法

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我长期在生源较差的学校从事物理教学,在多年的教学中用以下方法,集中学生有意注意,启迪学生思维,取得了一定效果.1 增强演示实验的趣味性例如,在讲大气压强时,我将马德堡半球中的空气抽出后,请班上公认的“大力士”上来对拉,他俩的“无能为力”引起大家的有意注意.这时,我将一只大漏斗,一块橡皮薄膜,一只抽气筒放在讲台上,问学生:“怎样用这些器材做一个类似的实验?”学生们十分活跃,争着回答.我综合学生的回答进行演示:将薄膜紧紧张在漏斗口,把抽气筒与漏斗联结起来,逐渐抽出漏斗内的空气,薄膜随之向漏斗凹进,且越凹越深.然后请一学生将薄膜拉出、恢复原样,只见他艰难地拉出后一放手,“啪”的一声薄膜又凹了进去,学生们的注意力很集中.这时,我用投影仪及时展示思考问题:(1)未抽气前,薄膜为什么是平的?(2)抽气后为什么薄膜凹进去? I have long been engaged in physics teaching in schools with poor students. In many years of teaching, the following methods were used to focus students’ attention on intent and enlighten students’ thinking and achieved certain results. 1 Enhancing the fun of demonstration experiments For example, when it comes to atmospheric pressure, After I pulled out the air in the hemisphere of Madebago, I asked the “Hercules” recognized in my class to pull up. Their “powerlessness” caused everyone’s intention to pay attention. At this time, I put a big funnel, a piece of rubber film. A pumping tube was placed on the podium and the students were asked, “How do you use these devices to do a similar experiment?” The students were very active and eager to answer. I responded with a comprehensive student’s answer to demonstrate: tighten the film tightly at the mouth of the funnel. The air pump is connected to the funnel, and the air in the funnel is gradually drawn out. The film is then recessed into the funnel and is deeper and deeper. Then a student pulls the film out and restores it. He only sees him pulling it out. After letting go, the film of “click” was retreated and the students’ attention was focused. At this time, I used the projector to show the questions in a timely manner: (1) Why was the film flat before pumping? (2) Why is the film recessed after pumping?
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